Fuel used for a gas turbine is broadly divided into oil fuel represented by light oil, kerosene, and heavy oil and gas fuel represented by natural gas and city gas, though in correspondence to the recent rise in fuel prices, there are possibilities of an increase in the demand of low-quality fuel of a lower price and further correspondence to various kinds of fuel is required.
For example, C heavy oil and heavy-duty oil which are low-quality fuel, compared with regular fuel, contain more impurities (Na, K, S) or (Na, K, S, V) in the fuel, so that on high-temperature members composing a gas turbine such as movable blades and static blades with which high-temperature combustion gas generated when low-quality fuel containing these impurities is burnt makes direct contact, due to an alkaline sulfate and a V compound caused by the aforementioned impurities, high-temperature corrosion is easily caused.
The alkaline sulfate and V compound are of the highest corrosiveness in a molten salt (liquid phase) state and moreover, high-temperature corrosion caused on the high-temperature members of the gas turbine due to the molten salt, compared with high-temperature oxidation by regular fuel, progresses at an extremely fast speed, so that it is a very important problem for the lifetime management of the high-temperature components such as the movable blades and static blades used for the gas turbine.
As a prior art for preventing high-temperature corrosion due to molten salt, although aiming at gasified fuel obtained by gasifying coal, as a prevention measure for high-temperature corrosion due to the impurities contained in the gasified fuel, in Japanese Patent Laid-open No. Hei 01 (1989)-299621, the prior art for preprocessing gasified fuel to desulfurize or dealkalize it, removing impurities in the gasified fuel, and then supplying it to the turbine is disclosed.
Further, in Japanese Patent Laid-open No. 2002-297710, the prior art for predicting deterioration of the high-temperature members composing the gas turbine by high-temperature combustion gas and supporting the maintenance plan of a power generation plant is disclosed.